UV ink printing field and printing process adaptability

UV ink refers to an ink that is instantly cured by UV light exposure. The main components of UV inks include pigments, lysogenes, monomers (active thinners), light triggers and various additives. Among them, resins and active thinners play a role in fixing pigments and providing film-forming properties; The pigment gives the ink a moderate color and the cover force of the seal; Light triggers require that photons can still be absorbed to trigger polymerization under the interference of pigments,
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From the printing process, UV ink fast fixation speed, conjunctivation performance is good, all kinds of printing materials have good adhesion, and scratch resistance, wear resistance, acid resistance, alkalinity and other properties are better than ordinary ink, therefore, although its price is much more expensive than ordinary ink, but it is widely used.
currently using UV ink printing in the following fields:
1. Non-absorbent material printing
e.g. polyethylene (PE) film, PVC film, polypropylene (PP) film, foil and non-absorbent special materials. If these printing materials are printed with ordinary solvent-based inks, it will take a certain amount of drying time, usually also need to use powder spray, drying device or add other additives to the ink, and UV ink is completely free of such trouble.
2. Metal material printing
can shorten the curing process and simplify the original curing device when printing UV ink on the surface of the metal material. At the same time, the good curing and conjunctivation of UV ink surface can not only improve the post-press processing characteristics, but also improve the appearance quality of the product.
3. Commercial paper printing
commercial paper printing using printing materials and inks are more special, such as carbon-free copy paper, thermal paper, magnetic ink, anti-counterfeiting ink, etc. , and require inks with a certain degree of color change, heat resistance and stability, so it is best to use UV ink or UV light oil. At the same time, due to the fast bill printing equipment, ink use is small, but also with the use of UV ink printing advantages.
UV printing process adaptability is
1.UV printing (offset version)
offset printing according to the status of the substrate can be divided into a single sheet of paper offset and roll paper wheel transfer offset printing, single sheet of paper offset printing suitable for paper, cardboard, plastic sheet and foil printing; Rotating offset printing speed is fast, suitable for large quantities of books, newspapers, business forms and stickers printing. The use of UV ink in offset printing, mainly consider the following aspects: non-absorbent printing material ink curing; Ink emulsification may hinder the attachment of ink and insemination; Rotating press speed, requires ink curing speed and printing speed to match, especially sticker printing and the use of special ink securities printing, UV ink printing effect is better than resin offset ink.
offset printing for fine product printing, UV curing can reduce the loss of small outlets, improve the ink transfer rate of overprinting. When selecting ink raw materials, the influence of each part on UV ink should be considered to ensure the best printing results. Because offset ink film is generally 2 to 3 m, although it is good for light curing, but the ink film thin, pigment on the covering force of the printing surface will be affected, so generally to improve the pigment content in the formula; And increase the pigment content, ink film light transmission performance will be reduced, not conducive to UV curing; And the ink film itself is thin, if the wetting of pigment is not good, pigments, fillers are easy to be exposed to the surface of the ink film, affecting the gloss of the ink film, so choose a better dispersion of pigments. The following points should also be noted when using UV offset printing.
(1) Substations of different properties should choose different inks, taking into account the light transmission, curing rate, ink cover and gloss of the surface of the print.
(2) In color printing, the ability of various pigments to absorb UV photons is different, and their passing rate is from high to low for M, Y, C, BK, so the curing degree of various inks is also different. The passing rate directly affects the excitation energy of photons to the light trigger, so it is advisable to rank the printed color sequence as BK, C, Y, M, so that the ink with poor light transmission absorbs as many photons as possible, enhancing its curing effect.
(3) the use of alcohol moisturizing system can reduce the surface pressure of the ink, promote curing effect, and in the printing process, you can use the wetting fluid to the plate dredging area (blank part) for intensive treatment, to ensure that the pro-oil area is fully pro-ink, hydrophobic area is not ink.
Improve the ink formula and add the corresponding additives can increase the hydrophobicity of the ink, but too hydrophobic will lead to image edge ink shrinkage, fine level loss, network boundary is not clear, etc., affecting the quality of the print.
(4) UV printing on the paper surface strength requirements are high, surface strength is not easy to pull hair failure, with gold, silver paper jam printing, because of this kind of paper surface smooth, ink affinity is small, the second color overprinting is easy to pull off the first color ink. Therefore, in UV printing, the paper with high surface pressure should be selected, and the color sequence should be arranged reasonably, and the relevant process parameters in the printing process should be adjusted to avoid and reduce the occurrence of the above phenomenon.
2.UV printing (flexible version)
flexible plate printing is a printing process that has developed rapidly in recent years, the printed part is higher than the non-text part, and has elasticity, can better express the subtle layers and contours of the text part. In addition, its application of printing materials are very extensive, in addition to traditional paper, some non-absorbent printing materials, such as plastic film, aluminum foil composite paper, glass paper, etc. can also be used flexible printing.
the use of UV ink for flexible printing, in addition to should pay attention to coloring, curing and adhesion and other issues, but also must pay attention to the ink parts on ink viscosity, fluidity, in order to obtain better printing suitability and stability.
flexible printing process determines that the UV ink used should not have a high viscosity. Traditional flexible printing inks have solvent-based and water-based two, need to use a large number of solvents or water to adjust the viscosity, due to the use of a large number of solvents, most flexible printing inks in the fluidity is similar to Newtonian fluid, will lead to ink subsidion, instability, so give flexible printing ink appropriate tentacleability can prevent pigment flocculation.
UV flexible printing ink is an active thinner to reduce the viscosity of the system, therefore, its viscosity may be generally higher than solvent-based flexible printing ink. Although the viscosity of UV flexible printing inks is lower than that of mesh and offset inks, the addition of pigments will improve viscosity, especially when the pigment is wet, dispersed and stable. In addition, the effect of pigments on ink fluidization is more important, appropriate tentacles are beneficial, because when the molecular crosslinking inside the ink reaches a certain degree and false plasticity occurs, there is no pigment dispersion stabilizer ink system, in the high-speed operation of the ink roller, viscosity will drop sharply, but out of the ink roller into the relatively low rate of printing site, the viscosity will quickly rebound, for the printing surface wetting effect is too poor, not suitable for printing. The ink containing the appropriate dispersion stabilizer has a certain stability, and its own viscosity is not high, after high shearing, the viscosity recovery is also relatively slow, printing adaptability is better. 3.UV printing (screen)
UV printing (screen) ink solid content of 100%, there is no component volatilization, solidified ink film thickness basically unchanged, is conducive to obtain a higher film thickness, printing and curing process easy to control, can avoid blocking, spots and other failures, reduce downtime.
although UV mesh printing has many advantages, but the determination of light trigger conditions, affecting the curing quality of the ink layer, improper choice, but also in the surface of the ink film curing faster. On the other hand, UV mesh printing has its advantages, that is, although the ink film is thick, but the lower pigment content can achieve a high cover force, which is favorable conditions for the bottom curing. Without impeding pigment saturation and covering force, the proper addition of reflective light-transmission fillers, increase the concentration of light-transmission medium in the ink layer, but also help to improve the absorbance of the underlying trigger. Because the mesh ink film thick, printing accuracy is not very high, pigment particle size can be larger, so in the premise of not sacrificing pigment dispersion, can appropriately increase pigment particle size, so that the actual light transmission of ink increased, in order to benefit the bottom curing.
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